Waaay TMI, but I need backup!

I went to the gmail sign-in page on my significant other's Kindle Fire, and as I started typing in my info, an unfamiliar email address ([email protected]) was auto-populated for me. I tried to sign in just for the hell of it but the password wasn't saved. "John" said that he had never heard of that email address before and had no idea where it came from. Maybe a week or so later, the same thing happened again, but the email address was my 6 year old son's first and last name, followed by the number 68. This time the password had been saved so I logged in. It looked like the account was new and hadn't been used yet, but some settings we're in place. specifically that the backup account was London-based68. Again, "John" said that he had never heard of either address. Am I correct in thinking that he 100% had to have created both accounts?